Merge branch 'jc/checkout-m-twoway' into maint

* jc/checkout-m-twoway:
  t/t2023-checkout-m.sh: fix use of test_must_fail
  checkout_merged(): squelch false warning from some gcc
  Test 'checkout -m -- path'
  checkout -m: no need to insist on having all 3 stages

builtin/checkout.c

@@ -114,16 +114,21 @@ static int check_stage(int stage, struct cache_entry *ce, int pos)
 		return error(_("path '%s' does not have their version"), ce->name);
 }
 
-static int check_all_stages(struct cache_entry *ce, int pos)
+static int check_stages(unsigned stages, struct cache_entry *ce, int pos)
 {
-	if (ce_stage(ce) != 1 ||
-	    active_nr <= pos + 2 ||
-	    strcmp(active_cache[pos+1]->name, ce->name) ||
-	    ce_stage(active_cache[pos+1]) != 2 ||
-	    strcmp(active_cache[pos+2]->name, ce->name) ||
-	    ce_stage(active_cache[pos+2]) != 3)
-		return error(_("path '%s' does not have all three versions"),
-			     ce->name);
+	unsigned seen = 0;
+	const char *name = ce->name;
+
+	while (pos < active_nr) {
+		ce = active_cache[pos];
+		if (strcmp(name, ce->name))
+			break;
+		seen |= (1 << ce_stage(ce));
+		pos++;
+	}
+	if ((stages & seen) != stages)
+		return error(_("path '%s' does not have all necessary versions"),
+			     name);
 	return 0;
 }
 
@@ -150,18 +155,27 @@ static int checkout_merged(int pos, struct checkout *state)
 	int status;
 	unsigned char sha1[20];
 	mmbuffer_t result_buf;
+	unsigned char threeway[3][20];
+	unsigned mode = 0;
+
+	memset(threeway, 0, sizeof(threeway));
+	while (pos < active_nr) {
+		int stage;
+		stage = ce_stage(ce);
+		if (!stage || strcmp(path, ce->name))
+			break;
+		hashcpy(threeway[stage - 1], ce->sha1);
+		if (stage == 2)
+			mode = create_ce_mode(ce->ce_mode);
+		pos++;
+		ce = active_cache[pos];
+	}
+	if (is_null_sha1(threeway[1]) || is_null_sha1(threeway[2]))
+		return error(_("path '%s' does not have necessary versions"), path);
 
-	if (ce_stage(ce) != 1 ||
-	    active_nr <= pos + 2 ||
-	    strcmp(active_cache[pos+1]->name, path) ||
-	    ce_stage(active_cache[pos+1]) != 2 ||
-	    strcmp(active_cache[pos+2]->name, path) ||
-	    ce_stage(active_cache[pos+2]) != 3)
-		return error(_("path '%s' does not have all 3 versions"), path);
-
-	read_mmblob(&ancestor, active_cache[pos]->sha1);
-	read_mmblob(&ours, active_cache[pos+1]->sha1);
-	read_mmblob(&theirs, active_cache[pos+2]->sha1);
+	read_mmblob(&ancestor, threeway[0]);
+	read_mmblob(&ours, threeway[1]);
+	read_mmblob(&theirs, threeway[2]);
 
 	/*
 	 * NEEDSWORK: re-create conflicts from merges with
@@ -192,9 +206,7 @@ static int checkout_merged(int pos, struct checkout *state)
 	if (write_sha1_file(result_buf.ptr, result_buf.size,
 			    blob_type, sha1))
 		die(_("Unable to add merge result for '%s'"), path);
-	ce = make_cache_entry(create_ce_mode(active_cache[pos+1]->ce_mode),
-			      sha1,
-			      path, 2, 0);
+	ce = make_cache_entry(mode, sha1, path, 2, 0);
 	if (!ce)
 		die(_("make_cache_entry failed for path '%s'"), path);
 	status = checkout_entry(ce, state, NULL);
@@ -252,7 +264,7 @@ static int checkout_paths(struct tree *source_tree, const char **pathspec,
 			} else if (stage) {
 				errs |= check_stage(stage, ce, pos);
 			} else if (opts->merge) {
-				errs |= check_all_stages(ce, pos);
+				errs |= check_stages((1<<2) | (1<<3), ce, pos);
 			} else {
 				errs = 1;
 				error(_("path '%s' is unmerged"), ce->name);

t/t2023-checkout-m.sh

@@ -0,0 +1,49 @@
+#!/bin/sh
+
+test_description='checkout -m -- <conflicted path>
+
+Ensures that checkout -m on a resolved file restores the conflicted file'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	test_tick &&
+	test_commit both.txt both.txt initial &&
+	git branch topic &&
+	test_commit modified_in_master both.txt in_master &&
+	test_commit added_in_master each.txt in_master &&
+	git checkout topic &&
+	test_commit modified_in_topic both.txt in_topic &&
+	test_commit added_in_topic each.txt in_topic
+'
+
+test_expect_success 'git merge master' '
+    test_must_fail git merge master
+'
+
+clean_branchnames () {
+	# Remove branch names after conflict lines
+	sed 's/^\([<>]\{5,\}\) .*$/\1/'
+}
+
+test_expect_success '-m restores 2-way conflicted+resolved file' '
+	cp each.txt each.txt.conflicted &&
+	echo resolved >each.txt &&
+	git add each.txt &&
+	git checkout -m -- each.txt &&
+	clean_branchnames <each.txt >each.txt.cleaned &&
+	clean_branchnames <each.txt.conflicted >each.txt.conflicted.cleaned &&
+	test_cmp each.txt.conflicted.cleaned each.txt.cleaned
+'
+
+test_expect_success '-m restores 3-way conflicted+resolved file' '
+	cp both.txt both.txt.conflicted &&
+	echo resolved >both.txt &&
+	git add both.txt &&
+	git checkout -m -- both.txt &&
+	clean_branchnames <both.txt >both.txt.cleaned &&
+	clean_branchnames <both.txt.conflicted >both.txt.conflicted.cleaned &&
+	test_cmp both.txt.conflicted.cleaned both.txt.cleaned
+'
+
+test_done